Comparative effects of isoproterenol and dopamine on myocardial oxygen consumption, blood flow distribution and total body oxygen consumption in conscious lambs with and without an aortopulmonary left to right shunt.
OBJECTIVE
We sought to study the effects of catecholamines on myocardial oxygen consumption (VO2), regional blood flows and total body VO2 in lambs with circulatory congestion.


BACKGROUND
Catecholamines are often used to support cardiovascular function in children with circulatory congestion because they increase contractility as well as heart rate. However, these changes increase myocardial oxygen demand and thus can lead to a mismatch between myocardial oxygen supply and demand. Catecholamines can also change regional blood flows and VO2 unfavorably.


METHODS
We infused isoproterenol (0.1 microg/kg body weight per min) and dopamine (10 microg/kg per min) and measured myocardial and total body VO2 and regional blood flows in chronically instrumented 7-week old lambs with and without a left to right shunt.


RESULTS
Isoproterenol increased myocardial VO2, parallel to the increase in heart rate. However, myocardial blood flow and, consequently, oxygen supply also increased. This increase outweighed the increase in myocardial VO2, so that myocardial oxygen extraction decreased. Isoproterenol did not change blood flow distribution. Isoproterenol increased total body VO2; however, systemic oxygen supply increased even more, so that oxygen extraction decreased and mixed venous oxygen saturation increased. In contrast, dopamine had no or little effect on myocardial VO2 or blood flow distribution.


CONCLUSIONS
We conclude that the catecholamines isoproterenol and dopamine do not lead to a mismatch between myocardial oxygen supply and demand, nor do they change blood flow distribution unfavorably in 7-week old lambs with a left to right shunt. We demonstrated that isoproterenol is superior to dopamine, because it shifts the balance between oxygen supply and consumption toward supply so that systemic oxygen extraction reserve increases.
Bartelds
B
B
Beatrix Children's Hospital, University of Groningen, The Netherlands.
Gratama
J W
JW
Meuzelaar
K J
KJ
Dalinghaus
M
M
Koers
J H
JH
Heikens
W F
WF
Zijlstra
W G
WG
Kuipers
J R
JR
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery; D001775:Blood Circulation / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D019917:Blood Vessel Prosthesis Implantation; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects*; D004298:Dopamine / Q000494:pharmacology*; D004374:Ductus Arteriosus, Patent / Q000503:physiopathology*; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects*; D011651:Pulmonary Artery / Q000601:surgery; D011652:Pulmonary Circulation / Q000187:drug effects; D011654:Pulmonary Edema / Q000503:physiopathology; D012079:Renal Circulation / Q000187:drug effects; D012756:Sheep; D013318:Stroke Volume / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D002316:Cardiotonic Agents; D007545:Isoproterenol; D010100:Oxygen; D004298:Dopamine